A light emitting diode (LED), known as a next generation light source, has many positive attributes such as a relatively long lifespan, low power consumption, a rapid response rate, environmentally friendly characteristics, and the like, as compared with a light source according to the related art, and has been used as an important light source in various products such as illumination devices and back light units for display devices. In particular, Group III nitride-based LEDs including GaN, AlGaN, InGaN, InAlGaN, and the like have been used in semiconductor light emitting devices outputting blue or ultraviolet light.
In general, a reflective layer is formed under an LED chip and light is emitted upwardly and from four sides thereof, that is, the front, the rear, left and right of the LED chip, and therefore, when a light emission color is changed using a phosphor material, it may be an important issue to coat an upper surface of a chip and four sides thereof with a phosphor material to have a uniform thickness in order to secure a uniform quality of light. Thus, various conformal LED chip coating techniques have been proposed, but since a majority of the techniques are applied prior to a wire bonding process, the application thereof are limited to a flip-chip type package or an additional process is required to open a separate wire bonding pad part during phosphor coating. Further, such a technique is used in a free mold lead frame-type packaging process and may be difficult to be applied to a case in which a phosphor is coated with respect to individual chips.
As a packaging method in which a phosphor is coated after a bonding process is completed, there is a dispensing process in which phosphor particles are dispersed in a resin having high heat resistance and light transmission to produce a paste phase and a minute amount thereof is ejected through a nozzle having a predetermined diameter to then coat the entire chip with phosphors. In this process there is a need to appropriately maintain a viscosity adjusted between phosphor particles and a resin in order to eject an appropriate amount of micro liquid droplets. Here, a solid phase of inorganic phosphor particles have partial sedimentation during a coating process, even after being dispensed, until a phosphor paste is cured, due to a relatively low viscosity being required for implementation of the coating process, within a tube storing matters in equipment, and therefore, dispersibility of phosphor particles may be deteriorated in a resin, and light scattering may be increased.